This invention relates to an alkoxylation process in which one or more alkylene oxides are reacted with one or more compounds having active hydrogen atoms in the presence of a catalytically effectively quantity of the compound barium phosphate. In certain preferred embodiments, the invention relates to processes for the preparation of alkoxylate products having utility as nonionic surfactants.
A large variety of products useful, for instance, as nonionic surfactants, wetting and emulsifying agents, solvents, lubricants and chemical intermediates, are prepared by the addition reaction (alkoxylation reaction) of alkylene oxides (epoxides) with organic compounds having one or more active hydrogen atoms. For example, particular mention may be made of the alkanol ethoxylates and alkyl-substituted phenol ethoxylates prepared by the reaction of ethylene oxide with aliphatic alcohols or substituted phenols of about 6 to 30 carbon atoms. Such ethoxylates, and to a lesser extent corresponding propoxylates and compounds containing mixed oxyethylene and oxypropylene groups, are widely employed as nonionic detergent components of cleaning formulations for use in industry and in the home. As another example, the addition reaction of propylene oxide with polyols provides intermediates for the preparation of polyurethane products.
An illustration of the preparation of an alkanol ethoxylate (represented by formula III below) by addition of a number (n) of ethylene oxide molecules (formula II) to a single alkanol molecule (formula I) is presented by the equation ##STR1## A given alkoxylation process typically results in the production of a mixture of alkoxylate molecules having different numbers of alkylene oxide molecules, e.g., molecules having different values for the adduct number "n" in formula III in the above illustration.
The present invention particularly relates to an alkoxylation process wherein the alkylene oxide addition reaction is catalyzed by the compound barium phosphate, Ba.sub.3 (PO.sub.4).sub.2.
Various compounds of barium and of the other alkaline earth elements are known as alkoxylation catalysts. For instance, it has been reported (e.g., in U.S. Pat. Nos. 3,752,857, No. 4,134,854, No. 4,223,164, No. 4,306,093 and No. 4,239,917, and in published European Patent Applications 0026544, 0026546, and 0026547) that certain compounds of barium, strontium, and calcium catalyze alkoxylation reactions. U.S. Pat. No. 4,210,764 describes the use of cresylic acids to further promote alkoxylation catalyzed by barium compounds. U.S. Pat. No. 4,302,613 discloses catalyst systems which combine barium and strontium compounds with co-catalysts such as calcium oxide, calcium carbide, calcium hydroxide, magnesium metal, magnesium hydroxide, zinc oxide and aluminum metal.
Strong acids, including phosphoric acid, are also known as alkoxylation catalysts.
Of particular relevance to the present invention, U.S. Pat. No. 4,453,023 describes a process which employs a catalyst comprising a barium compound and a promoter selected from the class consisting of superphosphoric acid, phosphoric acid, diphosphoric acid, triphosphoric acid, phosphorous acid, dihydrogen phosphate compounds, oxides of phosphorous, carbon dioxide, and oxalic acid.